DE1520738A1 - Process for the preparation of polyhexamethylene adipic acid amide - Google Patents

Description

Process for the production of polyhexamethylene adipamide polyamides of the polyhexamethylene adipamide type are mainly used for production of textile fibers and molded articles -and were first used in the United States patent writings 2,130,523 and 2,130,943.

These polyamides are produced in two consecutive ways Reactions.

In all known processes for the production of polyamides from diamines and dicarboxylic acids, the diamine and the carboxylic acid are mixed to form an intermediate to obtain, in which the reaction components are essentially uncondensed State, and this ical product is then condensed to a polyamide, by heating it to a temperature at which condensation occurs quickly goes, wherein the water of reaction is removed from the reaction mixture.

There are extensive facilities for heating the polyamide which is formed necessary because the reaction mixture overheating due to the thermal instability in the boiler must be avoided. In addition, the poly @@ ii is used in As the reaction proceeds, it is viscous and does not conduct heat well.

As suggested in UK Patents @@ ift 614 625 and the French patent 963 936 is the polyanide by infrared radiation heated.

What is claimed is a process for the production of polyhexamethylene adipamide by mixing molten hexamethylenediamine with molten adipic acid, Evaporate the water from the reaction mixture and hold the reaction mixture in the molten state, which is characterized in that there is mixing of the reaction components at a temperature above 25C C.

The upper temperature limit is chosen so that the reaction mixture h not excessively contaminated by heat decomposition products, preferably during the Uischzeit the essential part of the water formed during the condensation removed from the reaction mixture, thereby polycondensing the reaction mixture and served in a molten state.

The manufacture of polyamides by directly heating a diamine with a dicarboxylic acid and subsequent heating to temperatures that are essential are above class temperatures, has already been mentioned in US Pat. No. 2,130 948 and 2,640,547. In this process, the starting substances are mixed obtain a product which, as will be shown below, is essentially unconverted is, whereby an effective utilization of the mixed heat during the condensation reaction not possible.

U.S. Patent 2,840,547 states that when using adipic acid subject to the usual polymerisation temperatures, largely ring formation occurs, creating a union of diamine with a dicarboxylic acid at these temperatures in the Melt polymerization process is made unfeasible.

In GebensatP for the teaching of US Pat. No. 2,540,547 it was found that polyhexamethylene adipamide by mixing the SchreXwen of hexamethylene diamine and adipic acid at the usual polymerization temperatures without extensive decomposition the adipic acid can be produced. There was also a method of control the molecular weight of the polyamide found, in which no significant interference durci decomposition reactions in the initial stages of j. olyaerisation or by losses occur due to evaporation of the diamine from the reaction mixture.

Example 1: 14, g of adipic acid are placed in a 250 ccm glass flask given that with a thermometer, a device for rinsing the apparatus with Nitrogen ~, a dropping funnel, the drain pipe of which extends to the bottom of the flask, and a distillation head connected to a condenser and a collecting vessel is provided.

After flushing the apparatus with nitrogen, 17.2 g of hexamethylenediamine are added added to the dropping funnel and heated to about 100 ° C. The adipic acid is melted and quickly heated to 25 ° C.

At the moment when the temperature of the acid reaches 250 ° a, According to the invention, the diamine is transferred from the dropping funnel to the within 20 seconds Given reaction flask. When the reactants are mixed, there is a violent, with Boil the reactant-linked reaction, with temperature first rises to 270 ° C and then rises 235 ° C falls after the excess of hexamethylene diamine is added. The temperature of the reaction mixture is brought according to the invention within 30 seconds to 300 ° C. and 2 11 minutes at kept this temperature.

Part of the reaction mixture is then rapidly dissolved in 200, 0, 3-benzyl alcohol given in a flask of known weight, the flask with a short, wide Air cooler is fitted and set to a temperature just below the boiling "un-t is heated at the point of the benzyl alcohol. The polymer dissolves quickly and the The flask with the polymer is weighed.

The concentration of the polymer in the solution found in this way is 6.7 g of the polymer per 1CO g of the solution.

23.7 g of the hot solution are mixed with 30 g of benzyl alcohol, the one Contains drops of phenolphthalein, dilute and the solution is heated and marked with 0, 126 N potassium hydroxide solution titrated in isopropanol. After adding 1.45 ml of the A very sharp transition point can be observed in the titration solution.

Another sample of the polyamide solution weighing 23.2 g is used with 25.0 g of phenol mixed. The mixture is made using 0.1 N HCl in isopropanol of a glass electrode-calomel electrode system is potentiometrically titrated. A sharp one End point is observed at 60 millivolts per 0.01 milliequivalent of the titration solution. This corresponds to 0.585 milliequivalents of amine in the sample. The condensate of the product will be analysed. The ketone content found is 0.125 millimoles.

From the above example it can be seen that the polymerization of the Melt by mixing the reactants at the usual polymerization temperatures can be carried out without decomposition. It became another attempt carried out, which differed from the one described above essentially only in the fact that that iron nails with a total surface area of 50 cm2 in the reaction flask with the adipic acid. Within 3 minutes they were 2.8 milliequivalents Ketone Generated. From this it is evident that under the conditions in which Amide is formed, iron catalyzes the ring formation of adipic acid.

Therefore, iron and other substances that have the same effect should be used not used in the reaction apparatus for the initial reaction stages of the synthesis will.

From the end group determination described above it follows that in the Polyhexamethylene adipic acid amide melt during the preparation of the solution 0.377 nillie equivalent of amino groups and 0.116 nillie equivalent of carboxylic acid groups per g of the polymeric product. Hence the average Molecular weight 4070 and the difference in the concentration of the amino and acid end groups 0.261 milliequivalents per gram of polymeric product.

To obtain a product with good fiber-forming properties, the difference in the concentration of the two types of end groups may be 0.15 milliequivalent Do not overshadow per g of polymeric compound.

It can be seen that the product obtained according to Example 1 thereby converted into a product that is suitable for the manufacture of fibers can be that a carboxylic acid is added to it and converted into the molecule by reaction is installed. So you could by adding 0.161 milliequivalents of a carboxylic acid a product with an end group difference of 0.100 per g of the polymeric product Milliequivalents are obtained per g of the polymer.

Example 2 Using the method and apparatus according to Example 1 is 17.2 g of molten hexane ethylenediamine at once su 14.6 g Adipic acid given beforehand quickly heated to 280 ° C was. A violent reaction occurs. The mixture is 2 minutes at 290 bis Maintained 310 ° C. The condensate contains 0.150 milliequivalents of ketone.

Examples 1 and 2 show that polyhexamethylene adipamide can be prepared without excessive decomposition of adipinic acid in cyclopentanone, by mixing hexamethylenediamine and adipic acid above 250 ° C. The result is unexpected in view of the well-known heat instability of adipic acid, as previously believed and as indicated in US Pat. No. 2,840,547 is - the use of this acid at temperatures below the usual polymerization temperatures limited.

It was found that the condensation reaction above 250 ° C is so fast that the competitive decomposition of adipic acid suppresses will.

Since in Examples 1 and 2 at least part of the cyclopentanone orden formed during the preheating of the adipic acid to the mixing temperature must be, the preheating of the products should be carried out as quickly as possible.

According to the process according to the invention, in a single reaction stage reaches a molecular weight in the range of thousands and the heat of mixing of the reaction components used to heat the polyamide that is being formed.

To compare the method according to the invention with the prior art Melting hexamethylenediamine and adipic acid are among those in the technique U.S. Patent 2,840,54? specified conditions mixed, according to those as well Melting a diamine and a dicarboxylic acid as starting materials for the Used in the manufacture of linear polyamides be, but the starting products are partially condensed in a temperature range that is below the range in which the starting materials are mixed released mixed heat can still be effectively used.

The following comparison test shows that it is not possible an essentially polycondition; ized product in a single stage of the S chenus of the reaction components according to the teachings of US Pat. No. 840,547 and that it is consequently not possible by this method to use the mixed heat for heating the polyimide formed and for evaporating the water of reaction.

Comparative experiment (method according to USA patent 2 840 547): Using the apparatus used in Example 1, 13.9 g of melt are obtained Hexamethylenediamine and 14.6 g of melted adipic acid quickly at one temperature below 220 ° C gemi-cllt. The reaction mixture is then 1 1/2 minutes between Maintained 220 and 230 ° C, water and excess hexamethylenediamine during this time distilled off from the reaction mixture.

10, 50 g of the reaction mixture are quickly added to 100 ml of water 50 ° C poured, the polymer is quickly precipitated.

The polymer is crushed and filtered off. It has an average Molecular weight of 1090.

The aqueous filtrate contains 0.97 g of dissolved solids, of which 0.182 g of adipic acid and 0.116 g of hexamethylenediamine and the remainder essentially from the monomeric, namely N- (6-aminohexyl) adipic acid monoamide consists. The aqueous filtrate contains only traces of the hexamer and higher polycondensation products.

It was found by analysis that the water-soluble component des in the comparative experiment obtained reaction product almost completely from the Starting products and the monomeric dianionium salt.

Since in the process of U.S. Patent 2,840,547 the reaction mixture is essentially water-soluble even 4 minutes after the smelling is complete, the mixed product obtainable according to this process exists exactly as with the other known processes in which a diamine is mixed with a dicarboxylic acid is, essentially from the starting materials and the monomers and is therefore of the product obtained by the process of the invention and im is essentially a polyamide, chemically different.

This conclusion is supported by the fact that in contrast to Examples 1 and 2, in which the mixing of a rapid formation of Steam is accompanied, in the above comparative experiment, water is not during the Mieohene, but only during the subsequent heating long out of the reaction mixture distilled off what shows there. the polycondensation rate itself between 220 and 230 ° C is only moderate.

Mixing temperatures below 230 ° C are therefore essential for effective use the mixed heat for heating the polyamide formed and for evaporating the water of reaction not suitable. In the process according to the invention, the biamin and the dicarboxylic acid are used preferably mixed between 270 and 300 ° 0. However, since the upper temperature limit, in which the raw materials are mixed without excessive decomposition can, of factors such as the stay time, the existence of hot spots and catalytic Depending on the effects of the vessel walls, temperatures above 300 ° G in. used in the process.

The use of high mixing temperatures is particularly advantageous, if an additive such as. B. added a matting agent to the reaction mixture will.

When comparing the amount of water of reaction passing over in The reactions of Examples 1 and 2 can be seen that the reaction rate increases very sharply in the temperature range between 250 and 310 ° 0. This suggests indicate that above 300 ° 0 polyamides with a molecular weight in the range of thousands can be established within seconds. Since the decomposition reaction of the length of time during which the reaction products are exposed to the heat and losses of reaction products due to the formation of cyclopentanone the conditions of example 2 were negligible, it is obvious, that the mixing temperature used can be much higher than 300 ° 0.

It has been found that the molar heat of mix in mixing Hexamethylenediamine and adipic acid at 167 ° C 34.7 kcal per mole and at 240 ° 0 32 kcal per mole.

If one knows the specific heat of the diamine and the dicarboxylic acid and the corresponding mixture temperatures, one can determine the scope and the reaction conditions determine for the method according to the invention.

For example, it has been found that 9.1 kcal are required for the Temperature of one mole of hexamethylenediamine from 170 ° to 280 ° 0 with the application of a sufficiently high pressure, for Increase prevention of evaporation see below.

To heat 1 mole of adipic acid around the same temperature range, 10.8 kcal are required.

If you have 1 mole of hexamethylenediamine and 1 mole of adipic acid for the preparation mixed with a polyamide, about 35 g of water are generated in the reaction, and to evaporate this amount of water at 280 ° C, about 13 kcal are required.

The sum of these amounts of heat is the amount of heat besides the with chemical processes in reaction agemisch associated amounts of heat that the reaction system must be supplied in order to be able to carry out a process in which of adipic acid and hexamethylenediamine is started at 170 ° C and polymeric adipamides at the end and gives water vapor at 280 ° C.

It is 32.9 kcal and is comparable to the amount of heat the hexamethylene diamine molten after investigations into mixing molar amounts and melted adipic acid are released.

These findings lead to the surprising conclusion that da3 when using the heat of mixing of the reaction components to heat the Reaction mixture during the formation of the molten polyamide products it basically is possible that derive from the low thermal conductivity of the polyamides Overcoming difficulties in full standing, while at the same time considerable Saving of thermal energy.

The inventive method is preferably carried out by mixing Hexamethylenediamine and adipic acid in one device for continuous execution such procedures are practiced.

Claim!

Claims (1)

Claim: Process for the production of polyhexamethylene adipamide by mixing molten hexamethylenediamine with molten adipic acid, Evaporate the water from the reaction mixture and hold the reaction mixture in the molten state, there is no indication that one can do that Mixing the reaction components at a temperature above 250 ° C undertakes.